Sewing machine



Aug.. 5, X947. H. A. LANDROCHE SEWING MACHINE 2 Sheets-Sheet l Filed May '7, 1945 QS 1 m Huhu# N O l ,WM Y f n a wm. ww. L @Vn nm A e w E uf, @vllil m #www C All@ 5, 1947..

Hz' A. LANDROCHE SEWING MACHINE Filed May 7, 1945 2 Sheets-Sheet 2 2BR @El OK SQ 2gb/RR @GQ z fe e y hi Azorne Patented Aug. 5, 1947 SEWING MACHINE Henry A. Landroche, Spencer, Mass., assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application May 7, 1945, Serial No. 592,334

4 claims. (ci. 11a-59) 'n The present invention relates to improvements in sewing machines and more particularly to a thread tensioning device intended for use rin a wax thread inseam chain-stitch sewing machine of the Goodyear type disclosed in United States Letters Patent No. 1,108,560, granted August 25, 1914, upon an application led in the name of Andrew Eppler, and United States Letters Patent No. 2,219,933, granted October 29, 1940, upon an application led in the name of Alfred R. Morrill, employing a curved hook needle, a looper, and a take-up which acts to pull the thread with a stitch setting strain around the shank of the needle while the needle engages the work.

Present-day inseam sewing practices usually include the attachment of a relatively heavy inflexible welt to a shoe by a chain-stitch seam passing through the marginal portion of the shoe upper and through a sewing rib on the insole of the shoe, with the exposed enchained loops of thread in the stitches lying in a groove formed in the welt to receive them. The welt is intended to be molded during sewing operations by the tension of the thread acting to bend the welt along the line of the stitch receiving groove, to cause the welt to conform with the angle between the sewing rib and the feather or'marginal portion of the insole. The tension of the stitches also causes the upper to be tightened to obtain a close-fitting conformation to a last on which the upper is sup-- ported. For these reasons, it is desirable to apply to the thread while setting each stitch as heavy a tension as is practicable within the limits of the ultimate breaking strength of the thread and the strength of the shoe parts operated upon.

.The stitch setting strain on the thread occurs while each loop surrounds the work engaging needle and is applied against a resistance offered by both friction and inertia in a thread tensioning wheel of common construction and mode of operation, secured to one end of a rotatable shaft, the other end of which carries a friction drum. In starting the wheel in rotation the resistance offered by inertia is highest and therefore the stitch isset atthat time.

Engaging the friction drum is a brake shoe provided with a felt lining for insuring uniform and reliable distribution of pressure against the drum. During operation of the machine, the pressure of the .brake shoe against the drum is increased to a maximum during that part of each sewing cycle in which a stitch is set, and is decreased while the needle is being retractedv with its loop of thread, to insure easy movement of the thread through the substance of the work, particularly 2 when increased thicknesses require vadditional supplies of thread. Also, as aresult of variations in sewing speed along different portions yof ashoe, the inertia of the tension wheel and drum may'cause the tension on the thread, while the stitches are being set, t0 vary substantially, sothat the machine is provided with a fly-ball governor for decreasing the pressure of the brake shoe on the drum at higher sewing speeds. Even with these forms of controlling devices for the tensioning wheel, when the machine is adjusted to operate with a sewing thread tension close to the breaking strength of the thread, irregular action frequently occurs from erratically changing coeflicients of friction between the friction drum and brake shoe. Thus, thread breakage and improperly molded welt along the inseam are not entirely avoided with the most carefully adjusted controlling mechanisrns. j

When a smooth finish is provided on the friction surface of the drum and a clean `felt lining is applied to the brake shoe, continuous satisfactory results may be obtained provided the stitch setting tension on the thread does not approach too close to its ultimate breaking strength. If too close an approach to the breaking strength of the thread is madefthe pressure on the friction` drum, together with the heat which is applied to the tension Wheel when hot Wax thread is employed, causes the surface of the felt lining to become glazed within a short time after being put to use in such a way as to result in excessive adhesion between the felt and the surface of the drum. With a glazed felt lining the coeicient of friction and the tension on the thread also tend to rise substantially as the velocity of thread withdrawal increases. Consequently, if a stitch is set at the tension in the thread required to start the tension wheel and drum against the forces of inertia from a position of rest as well as the frictional effect, the increasing frictional effect of the glazed felt lining on the drum as the lspeed of rotation increases after the stitch is set may cause thread breakage. If the pressure of the brake shoe on the drum is relieved to avoid breakage at the time of greatest frictional eiect, then there will be insufficient tension when the tension wheel starts its rotation to cause uniform setting of the stitches with the welt properly molded to the shoe.

There is often considerable variation between successive stitches in the amounts of thread required and, therefore, in the speed of rotation of -the tension wheel so that if a stitch is notfset be left relatively loose, or, if the friction of the drum is such as to insure proper setting of a stitch, then those stitches requiring more than the usual amounts of thread will cause rotation of the tension wheel at such high speeds that thread breakage Will occur sporadically as a result of a frictional effect increasing with speed of ro,- tation.

The object of this invention is to improve and render more uniform the operation of the thread tensioning devices in an inseam shoe sewing or other chain stitch machine in which sewing results Will be reliable under all conditions Without frequent replacement of brake shoe linings and to insure regular formation of tight stitches without variation or necessity of tension adjustments over long periods of machine operation. A feature of the invention, accordingly, consists in the pro-- vision of thread handling mechanism of the general type hereinbefore referred to, including a tensioning wheel and frictioning means therefor having a drum connected to be rotated with the wheel and a Vbrake shoe engaging the drum, in combination with means for avoiding variations in frictionai coefficient between the drum and the shoe as the result of change in the character of the frictional surfaces from wear, heat or accumulation of friction modifying materials. To these ends and as herein exemplied, there is applied to the friction drum a continuous surplus supply of friction modulating liquid so that instead of depending upon uncertain and irregular characteristics between the engaging friction surfaces, the tension on the thread after each stitch is set and after the tension wheel is started in rotation, will be controlled by the viscosity of the friction modulating liquid. Also, by the use of a friction modulating liquid, the viscosity effect of which does not vary substantially with heat or speed of relative movement, the tension on the thread. will not riseA to such an extent as to` cause thread. breakage under widely varying conditions of machine operationlFurthermore, whenever the friction Wheel is started from a position of rest during each sewing 'cycle the frictional eilect is reduced substantially because` a relatively heavy film. oi friction modulating liquid is built up. between the brake shoe and the drum as rotation starts, thus serving to` separate the brake shoe from direct frictional contact with the drum. In this Way each stitch is set against the resistance offered in starting the friction wheel in rotation without any possibility of substantial increase in friction or tension on the thread during continued rotation.

Other features of the invention reside in the novel devices, combinations, and arrangements of parts hereinafter described and claimed, the advantages of which will be obvious from the following` description taken in connection- With the drawings illustrating one embodiment of the invention.

In the drawings,

Fig. 1 is a side sectional view of a machine. embodying the inventionand illustrating a portion of a shoe in operating position looking from the left side of the machine;

Fig. 2 is a. detail plan view of a portion of the thread tension controlling mechanism of the machine illustrated in Fig. l;

Fig. 3r is a fragmentary sectional view on an enlarged scale of a shoe, after inserting the inseam, in which the threads are improperly tensioned' during sewing operations;

Fig. 4 is a similar view illustrating a properly inserted inseam, and

Fig. 5 is a diagrammatic view illustrating the variation in tension on the thread in the machine as the speed of thread Withdrawal increases during sewing under diierent operating conditions.

The. machine illustrated iny the drawings is intended for sewing together the welt, upper and insole of a Goodyear welt shoe and is similar to that shown and described in the patents above referred to. This machine is provided with the usual'` stitch forming devices including a hook needle l0, an awl H, a channel guide l2, a looper lli,4 a thread finger i6, a welt guide I8, a main takeup 20, an auxiliary takeup 22, a. tensioning wheel 24 and other work guiding and thread manipulating devices.

The welt is applied to the shoe in the form of a strip 26 of relatively heavy leather and is directed through the welt guide i8 to give it a trough shape generally to conform with the angle between the shoulder andmarginal flange of the insole indicated at 28, the upper 30 being carried into the angle with the welt as the stitches of the inseam are tightened. To insure accurate conformity of the upper to a last 32 supporting the shoe parts, a heavy tension must be applied to the thread While settingA each stitch, the proper setting of each stitch lbeing resisted by the tension of the upper about the last and the resistance to fiexure oiered by the welt against being drawn snugly against the rib and the insole. With present-day practices the size" of thread employed in the inseam is limited to that which will avoid formation of excessively largeperforations in the shoe parts. Excessively large .perforations tend to weaken the parts along the seam and with the' poorer qualities of' thread at present available it is dicult to insure an ade'- quately tight seam for this purpose. If the stitches of a seam are improperlyv tightened while being set the inseam will hold the shoe parts in an insecure manner so that when theshoe is completed there will be a tendencyfor the welt to-separate from the upper, exposing the threads of the inseam and resulting in a misshapen, badly appearing shoe.

In the seam illustrated in Fig. 3 of the drawings the stitchesl are illustrated as being tightened against the resistance offered by the welt and upper without `drawii'ig these parts of the shoe into accurate conformity with the angle between the rib and marginal portion of the insole so as to leave a gap of triangular section 34 at the root of the insole rib. Frequently with poorer qualities of sewing thread now obtainable it is impossible to tighten the stitches of an in'- seam suihciently to close up this gap without the use of special expediente such as preforming the welt with an angular shape before it is applied to the shoe or inserting special' temporary fastenings to hold the parts in proper relationship lbefore sewing the inseam. When properly sewn the parts will be brought into close register without gaps or voids between them, as illustrated in Fig. 4.

To impart proper sewing tension to the thread in an inseam shoe sewing machine it is customary to employ a thread having a tensile strength resistant to a forty or fifty-pound' pull, for ex'- ample, and in adjusting the sewing tension of the machine the frictional resistance oifered against withdrawal of the thread through the looper i4 may approach to within av few ounces of the ultimate breaking strength of the thread.

Thus, if there is any substantial degree of variation from one stitch to another of the tension applied to the thread by the tensioning wheel, thread breakage is certain to occur. If the frictional force of the tensioning wheel is reduced to avoid breakage then an improperly set inseam will result, as illustrated in Fig. 3.

The resistance offered by the tensioning wheel 24 in this type of sewing machine is regulated accordingly as carefully as possible to obtain most effective results and is controlled by a number of different mechanisms. The tensioning Wheel 24 is secured to a shaft 35 mounted for rotation in bearings in the machine frame. Also secured to the shaft 36 in front of the tensioning wheel, as illustrated in Figs. 1 and 2, is a friction drum 38 acted upon by a brake shoe 4!! of arcuate shape fitted with a lining 42 ofheavy felt or similar material. The brake shoe is pressed downwardly against the drum 38 and is pivotally mounted by a screw 43 on a lever 44, one end of which is fulcrumed at 45 on the frame of the machine. The upper surface of the brake shoe lever 44 has bearing against it a pair of adjustable abutments and 52 slidingly mounted lengthwise of a pair of individually spring pressed actuating levers 54 and 56, respectively. To adjust the tension, the abutments have threaded openings to receive adjusting screws 5l having suitable knurled heads rotatable in the levers.

The actuating levers 54 and 55 for the brake shoe are pivotally mounted at their rearward ends on a stud 58 fixed in the frame of the machine and at their forward ends the levers are forced downwardly by a tension rod El! slidingly mounted in a perforated lug 62 at its lower end and arranged to bear against a short bar 54 pivotally secured to the forward end of the lever 56. The bar 64 overlies the forward end of the lever 54, thus serving as a balance bar to distribute the downward pressure of the tension rod 60 to both levers. The upper end of the tension rod carries a spring compressed between a collar 66 on the rod and the perforated end of a speed controlled lever E8 through which i the upper end of the tension rod passes. The speed controlled lever is fulcrumed on a screw 'l0 carried Iby the forked upper end of a bracketV T2 having also mounted within it a fly ball governor 'I4 geared to rotate with the main sewing machine shaft indicated at 15. The arrangement is such that when the machine is running at relatively slow speeds a greater frictional resistance is imparted to the tensioning wheel than when running at higher speeds. at higher speeds the tension on the thread required to overcome the inertia of the tensioning wheel and friction drum is greater than when running at low speeds so that less friction ,on the drum is needed to supplement inertia in obtaining the desired degree of tension in the thread.

To enable easy formation of each stitch the full maximumpressure of the tension rod is partially relieved and does not act wholly against the lever 44 at all times during each sewing cycle. For this purpose the forward end of the actuating lever 54 overlies a pin 18 projecting laterally from a pivotally mounted block 80 having a recess 82 within which a tooth shaped projection 84 operates. The toothed projection 84 is mounted upon a lever 86 fulcrumed on a shaft 88 fixed in the machine frame and at its forward end the lever carries a roll 9D engaging a cam 92 on the sewing shaft 16. The cam lever 86 is so operated that the abutment 50 engages the When running 'thread tension as ordinates.

brake shoe supporting lever 44 only during that time when the takeup 20 is acting to set each stitch, the needle at this time engaging the work with each needle loop surrounding its shank. It is therefore at this time that the maximum tension is applied to the thread to tighten and set each stitch in such a way as to draw the welt and upper into close fitting conformity with the rib and marginal portion of the insole. After setting each stitch continued movement of the takeup causes an amount of thread to be withdrawn from the supply past the tensioning wheel sufficient for the succeeding stitch. If the frictional characteristic of the felt brake lining 42 on the drum 38 at this time is such as to increase the friction on the thread excessively, breakage of th'e thread is certain to occur.

After the setting of each stitch and during withdrawal of thread for the succeeding stitch by the takeup, the tensioning wheel rotates at a sufficient speed to deliver thread rapidly to the stitch forming devices, ranging upwardly to a velocity of 12()` inches of thread a second. The amount of thread actually used for each stitch' in the usual inseam sewing operation, however, is roughly an inch and a quarter so that rotation of the tensioning wheel is accelerated extremely rapidly and is stopped as nearly instantaneously as possible. With the best of control, however, there is some overthrow and slight variation in amount of thread drawn past the tensioning wheel between stitches. Consequently the speed of rotation of th'e tensioning wheel will vary correspondingly. The machine of the patents, above identified, is therefore designed in the manner described to set each stitch at the instant that the tensioning wheel begins to rotate so that a more uniform control of the stitch setting tension may be obtained. In that machine the desired results are obtained so long as the characteristic of friction between the brake sh'oe 40 and the drum 38 does not increase substantially with speed of tensioning wheel rotation. If a substantial increase of friction does occur it may impart sufficient tension to the thread to cause thread breakage without setting successive stitches in a seam with any degree of regularity.

According to an important feature of the present invention the illustrative machine is provided with means for preventing an increase in tension on the thread with increasing speed of rotation in the tensioning wheel by the application of a suitable supply of friction modulating liquid to the friction drum 38 to produce a uniform film between the drum and the shoe 40 during rotation. As illustrated in Fig. 5, three curves or lines denote variations in thread velocity or speed of tension 'wheel rotation as abscissae and in The line 94 illustrates the action of the tensioning wheel when the brake shoe 40 is equipped with a lining 42 of new clean felt properly fitted to conform with the curvature of the friction drum 38. It will be noted that this line starts from a fixed positive value of th'read tension and rises slightly as the speed of tensioning wheel rotation increases but not to such an extent as to cause the tension to 'rise above that required to overcome the linertia of the tension wheel and start it rotating, particularly when sewing at high speeds. So long as the felt lining is kept in clean, flexible condition acceptable sewing operations may be performed. However, during continued use of the machine the pressure of the brake shoe against the surface of the drum together with th'e substantial amount `of heat ordinarily applied to the par-ts causes the surface of the felt lining to become glazed in such a w-ay that there is a tendency for the drum to bind intermittently against the brake lining particularly as the speed of tensioning wheel rotation increases, as indicated in the curve 96. With the glazed surface on the lining, the thread tension, therefore, increases progressively with the speed of tensioning wheel rotation until eventually it causes a resultant tension exceeding that required to start the tensioning wheel in rotation. If the pressure on the drum has been adjusted to produce a stitch setting tension in the thread close to the breaking point of the thread when the tensioning wheel is started, then the increase of tension, such as indicated in the curve 96, will certainly cause thread breakage. Conversely if the pressure on the drum is reduced loose stitches will result.

According to the present invention friction modulating liquid is applied to the friction drum in the form of a bath 91 to provide a surplus quantity :thus insuring formation of a thicky film between the brake lining Yand the friction drum during each rotation. The frictional effect thus is caused to decrease abruptly as the tensioning wheel starts to rotate, as indicated at a in the curve 98, and as the speed of rotation of the tensioning wheel increases the characteristic of friction merges with that produced by the viscosity .1

of the liquid in the lm as the liquid is drawn by rotatie-nef the drum between the lining and the drum.l The viscosity characteristic of the film within the ordinary rotational speeds of the tensioning wheel never rises in actual practice above a frictional intensity produced by clean, unglazed felt, as indicated in the curve 94, so that with the present invention effective sewing operations may be Obtained even with the felt in a glazed condition inasmuch as the nlm is built up to separate the felt from the drum before a tensioning wheel speed is reached at which the glazed surface of the fel-t would cause excessive tension. Thus, with the friction modulating liquid on the brake drum, sewing operations may be continued indefinitely with eiective results regardless of the condition of a glaze on the felt surface. In this way having once adjusted the pressure of the brake shoe on the drum no further regulation of tension is required as a result of change in the character of the surface on the felt lining A2. The felt lining also may be used until entirely Worn away Without replacement.

For retaining a surplus supply of friction modulating liquid in contact with the drum lat all times a portion of the machine frame is built up in surrounding relation yto the brake drum to form a reservoir IUD, leaving a small segment of the friction drum which contacts with the brake shoe 49 exposed while providing access to the shoe to enable easy replenishment of the supply of liquid. The reservoir is filled sufciently to cause the lower circumference of thedrum to dip therein. Conveniently the liquid may consist of a good quality lubricating oil introduced within the reservoir Il to a sufficient depth to cause a surplus to be carried between the surface of the friction drum 3 and the brake shoe lil` Whenever the drum is rotated.

In order to shield the tension wheel and prevent contact of the liquid with the tension Wheel, the

wheel is enclosed within a shielding cover portion 102 of the frame and the reservoir is build up above the bearing for the shaft 36. In this way projection of liquid outside the reservoir by. entrainment with the drum as the wheel rotates is avoided. v

Having thus described my invention, what is claimed is:

1. A .chain-stitch sewing machine having stitchy forming devices including a hook needle and a looper, said devices acting to form and carry loops of needle thread through the work and to Withdraw thread from the supply for the succeeding stitch after applying a, stitch setting tension rto the thread, and a tensioning device comprising a thread engaging wheel, a friction drum connected to be rotated with the wheel, and a brake shoe engaging the drum, in combination with means for applying a, continuous surplus supply of friction-modulating liquid to the friction drum to prevent a substantial increase in tension on the thread while the thread for the succeeding stitch is being withdrawn.

2. A chain-stitch sewing machine having stitch forming devices including a hook needle and a looper, said devices acting to form and carry loops of needle thread through the work and to withdraw thread from the supply ,for the succeeding stitch after applying a stitch setting tension to the thread, and a tensioning device comprising a thread engaging wheel, a shaft to which the wheel is secured, a friction drum fast to the shaft, and a brake shoe engaging the drum, in combination with means for applying a continuous surplus supply of friction-modulating liquid to the drum and for shielding the wheel from contact with the liquid.

3. A chain-stitch sewing machine having stitch forming devices including a hook needle and a looper, said devices acting to form and carry loops of needle thread through the work and to withdraw thread from the supply for the succeeding stitch after` applying a stitch setting tension to the thread, and a tensioning device comprising a thread engaging wheel, a shaft to which the wheel is secured, a friction drum fast to the shaft, and a brake shoe engaging the drum, in combination with a reservoir into which the friction drum dips for applying a continuous surplus supply of friction modulating liquid to the drum.

4. A chain-stitch sewing machine having stitch forming devices including a hook needle and a looper, said devices acting to form andcarry loops of needle thread through the work and to Withdraw thread from the supply for the succeeding stitch after applying a stitch setting tension to the thread, and a tensioning device comprising a thread engaging wheel, a friction drum connected to be rotated with the thread engaging wheel, a brake shoe engaging the drum, and mechanism for pressing the brake shoe against the drum with varying degrees of pressure at different times in each sewing cycle to impart a maximum tension to the thread while each stitch is being set, in combination with means for applying a continuous surplus supply of friction modulating liquid to the drum. to prevent a substantial increase in tension on the thread in each sewing cycle after a stitch is set.

HENRY A. LANDROCI-IE. 

